Add python linked stack impl.

Author: michaeltcoelho

linked_stack/linked_stack.py

@@ -0,0 +1,50 @@
+from typing import Optional
+
+
+class Element:
+
+    def __init__(self, value: int) -> None:
+        self.value = value
+        self.next = None
+
+    def __str__(self) -> str:
+        return f'<Element(value={self.value})>'
+
+
+class LinkedStack:
+
+    def __init__(self, head: Optional[Element] = None) -> None:
+        self.head = head
+
+    def __str__(self) -> str:
+        current_element = self.head
+        elements = []
+        while current_element.next:
+            elements.append(str(current_element))
+            current_element = current_element.next
+        elements.append(str(current_element))
+        return str(elements)
+
+    def push(self, new_element: Element) -> None:
+        if self.head is None:
+            self.head = new_element
+        else:
+            new_element.next = self.head
+            self.head = new_element
+
+    def pop(self) -> Element:
+        old_head = self.head
+        self.head = old_head.next
+        return old_head
+
+
+if __name__ == "__main__":
+    first_el = Element(1)
+    second_el = Element(2)
+    third_el = Element(3)
+
+    linked_stack = LinkedStack(first_el)
+    linked_stack.push(second_el)
+    linked_stack.push(third_el)
+
+    assert linked_stack.pop() is third_el